Luminescent Metal-Organic Framework Mixed-Matrix Membranes from Lanthanide Metal-Organic Frameworks in Polysulfone and Matrimid

Metal-organic framework/polymer (MOF-polymer) mixed-matrix membranes (MMMs) have been prepared by embedding the luminescent lanthanide (Ln) MOFs (3)(infinity)[Sr(0.9)Eu(0.1)lm(2)] and (2)(infinity)[Tb2Cl6(bipy)(3)]center dot 2bipy (lm(-) = imidazolate, bipy = 4,4'-bipyridine) into polysulfone (PSF, Ultrason (R) 5) and Matrimid (R) polymer films. The successful embedding of the Sr and Eu MOFs has been achieved for both matrixes, and the original MOF luminescence is maintained. The defect-free nature of the membranes was proven by the slightly lower gas permeation of the MMMs with the dense filler particles. For the Tb-bipy MOF, successful embedding is possible for polysulfone only. For the preparation of the MOF polymer membranes, the influence of different mass fractions of the luminescent MOFs ranging from 8-16 wt.-% and preparation from suspensions with and without ultrasonic radiation were studied. The influence of the MOF fraction is different for both membrane materials. For the polysulfone, lower amounts of MOF are preferable and lead to an increase of the overall luminescence intensity, whereas the opposite was observed for Matrimid. Altogether, the parity-allowed emission of the Eu2+ ions is apparently stronger than the Tb3+ emission and leads to membranes with strong emission that is visible to the naked eye under normal daylight. Thereby, the Ln MOF polymer membranes open new options for the handling of luminescent MOFs.